you wot?
"a standard JavaScript library - generally lacking in JavaScript - to build large, complex web applications" ... ahem jQuery?
Google's critical mass online, combined with recent years' Web 2.0 fever, have helped consolidate 14-year-old JavaScript in the field of web development. Now Google has released some of the tools it used to build Gmail, Google Docs, and Google Maps that helped in that process of establishing JavaScript as a central player in …
"What's wrong with variety and choice in the hands of a developer? "
Well, for one thing, it means yet another library to learn and get used to. Have a search for web developer jobs now and you'll see many of them requiring experience with a specific library. Likewise PHP jobs. If you don't have experience with the framework (Symfony, Cake etc) an employer is looking for then you have little chance of getting the job.
Choice is good, but only up to a point.
JavaScript is perhaps one of the more intuitive programming languages, it is not that complicated.
Another layer of abstraction is just not needed, it is so easy to build your own abstraction to fit the task at hand then bother to rely on some form of pseudo generalised abstraction.
JavaScript libraries or toolkits just lead to bloat, instead you should create your own toolkit for the application if it warrants it.